In the construction of dry walls, as distinguished from plastered walls, panels or wall board usually formed of gypsum are nailed or stapled to the wall studs or ceiling joists. It is essential that the abutting margins of coplanar panels as well as angular, usually 90.degree., related panels be covered and bonded together. This is usually accomplished by a paper tape having a coating of a viscous mixture with adhesive properties, identified in the trade as "mud" or "dry wall mud."
Usually the tape is manually coated with the mud and manually applied to the margins of adjacent panels, with the aid of hand tools. Automatic machines for coating and applying such tapes have been developed; however, such machines have been difficult to operate, requiring considerable practice before the user can become proficient.